On Wed, 07 Feb 2007 14:57:27 +0100 Steven Scholz <[EMAIL PROTECTED]> wrote:
> Alan, > > >>> Only relevant for DMA really > >> So rqsize is only needed for DMA accesses? > > > > PIO transfers are sector at a time, or multi-sector up to a usual limit > > of about 16 sectors. > > So again: rqsize does not matter for PIO transfer? > > Looking at the lines > > if (hwif->no_lba48_dma && lba48 && dma) { > if (block + rq->nr_sectors > 1ULL << 28) > dma = 0; > else > lba48 = 0; > } This code is for DMA transfers when we need LBA48 and can't do it. The general code tries to avoid LBA48 commands when possible as they require two loads of the taskfile which has a performance impact. The old IDE code didn't use to do this for PIO that I remember but I'd need to re-read the code in case it ever got changed. If it doesn't its not hard to add a check for the PIO case. - To unsubscribe from this list: send the line "unsubscribe linux-ide" in the body of a message to [EMAIL PROTECTED] More majordomo info at http://vger.kernel.org/majordomo-info.html